In recent years, a technique of forming a thin film transistor (TFT) using a semiconductor thin film (with a thickness of approximately from several nm to several hundreds nm), which is formed over a substrate with an insulated surface, has been attracting attention. The thin film transistor has been widely applied in various electronic devices such as an IC and an electronic apparatus. In particular, development related to the thin film transistor as a switching element for a liquid crystal panel and a light emitting display panel has been hurried.
With respect to a liquid crystal display panel, a liquid crystal material is sandwiched between an element substrate and an opposing substrate. Here, TFTs using amorphous silicon or polysilicon as semiconductors are arranged in matrix, and pixel electrodes, source wirings and gate wirings connecting to each TFT are formed over the element substrate respectively. The opposing substrate having an opposing electrode is placed opposite to the element substrate. Further, a color filter for color display is formed over the element substrate or the opposing substrate. Polarizing plates are then arranged over the element substrate and the opposing substrate as optical shutters, respectively, to display color images.
The color filter of the liquid crystal display device has colored layers consisting of R (red), G (green), B (blue), and a light shielding mask (black matrix) covering gaps between pixels, and extracts red light, green light, and blue light by transmitting light therethrough. A light shielding mask for the color filter is generally made from a metal film or an organic film containing a black pigment. The color filter is arranged at a position corresponding to the pixels, thereby being capable of changing the colors of light to be extracted for each pixel. Note that, the position corresponding to the pixels indicates a position that accords with a pixel electrode.
With respect to a light emitting display device, there are a colorizing method by arranging light emitting elements that emit red light, green light, or blue light in matrix; a coloring method by utilizing a color filter with use of a light emitting element that emits white light; and the like. The colorizing method by utilizing the color filter with use of the light emitting element that emits white color is similar to a colorizing method for a liquid crystal display device using a color filter in principle (see patent document 1).
[Patent document 1]: Japanese Patent Application Laid-Open No. 2001-217072